/*
 * Copyright 2012-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cn.springcloud.gray.bean.properties.bind;

import java.util.Collection;
import java.util.List;
import java.util.function.Supplier;

import cn.springcloud.gray.bean.properties.bind.Binder.Context;
import cn.springcloud.gray.bean.properties.source.ConfigurationPropertyName;
import org.springframework.core.CollectionFactory;
import org.springframework.core.ResolvableType;

/**
 * {@link AggregateBinder} for collections.
 *
 * @author Phillip Webb
 * @author Madhura Bhave
 */
class CollectionBinder extends IndexedElementsBinder<Collection<Object>> {

    CollectionBinder(Context context) {
        super(context);
    }

    @Override
    protected Object bindAggregate(ConfigurationPropertyName name, Bindable<?> target,
                                   AggregateElementBinder elementBinder) {
        Class<?> collectionType = (target.getValue() != null) ? List.class
                : target.getType().resolve(Object.class);
        ResolvableType aggregateType = ResolvableType.forClassWithGenerics(List.class,
                target.getType().asCollection().getGenerics());
        ResolvableType elementType = target.getType().asCollection().getGeneric();
        IndexedCollectionSupplier result = new IndexedCollectionSupplier(
                () -> CollectionFactory.createCollection(collectionType,
                        elementType.resolve(), 0));
        bindIndexed(name, target, elementBinder, aggregateType, elementType, result);
        if (result.wasSupplied()) {
            return result.get();
        }
        return null;
    }

    @Override
    protected Collection<Object> merge(Supplier<Collection<Object>> existing,
                                       Collection<Object> additional) {
        Collection<Object> existingCollection = getExistingIfPossible(existing);
        if (existingCollection == null) {
            return additional;
        }
        try {
            existingCollection.clear();
            existingCollection.addAll(additional);
            return copyIfPossible(existingCollection);
        } catch (UnsupportedOperationException ex) {
            return createNewCollection(additional);
        }
    }

    private Collection<Object> getExistingIfPossible(
            Supplier<Collection<Object>> existing) {
        try {
            return existing.get();
        } catch (Exception ex) {
            return null;
        }
    }

    private Collection<Object> copyIfPossible(Collection<Object> collection) {
        try {
            return createNewCollection(collection);
        } catch (Exception ex) {
            return collection;
        }
    }

    private Collection<Object> createNewCollection(Collection<Object> collection) {
        Collection<Object> result = CollectionFactory
                .createCollection(collection.getClass(), collection.size());
        result.addAll(collection);
        return result;
    }

}
